Process FASTA file to output header and all matching subsequences

Question

I need to search a FASTA file for certain regions of the DNA sequence. For each match, I need to print the sequence header followed by all matches within that sequence. I want to print the header once followed by the matching sections.

The output of the following code is close, but the matched regions of DNA are printed above their header instead of beneath it. I cannot flip the two blocks of code because that cuts off the first results.

# First, I open my file and print a warning if it fails.
unless ( open FILE, "<", '/scratch/SampleDataFiles/test.fasta' ) {
    die "Sorry", $!;
}

$/ = ">";    # This changes the record separator from \n to >, so I can chomp it later.

my @file = <FILE>;
my $file = "@file";
chomp $file;

# To view the file I can--
# print $file;

my $count = 0;    # here I will count the matched regions

my $sequence_count = 0;    # here I will count the sequences
                           # that contain a matched region

foreach $file ( @file ) {

    # I look for each header and its following sequence
    # And count the total sequences in the file
    if ( $file =~ /(.*;.*;?\n)(\w+)/ ) {

        my $head     = $1;
        my $sequence = $2;

        $sequence_count = $sequence_count + 1;

        # Now, I use the sequences I matched and search for a
        # hydrophobic region

        while ( $sequence =~ /([VILMFWCA]{8,}?)/gi ) {

            # I want to know what the position of the match is
            my $pos = pos( $sequence ) - 7;

            print "\n", $1, " found at ", $pos;
        }

        # I use the count variable I made earlier to count up each
        # time I match a sequence that has one or more hydrophobic region

        if ( $sequence =~ /([VILMFWCA]{8,}?)/gi ) {

            print "\n",
                    "Hydrophobic region(s) found in ",
                    $head,
                    "\n",
                    "-------------------------------------",
                    "\n";

            $count = $count + 1;
        }

    }
}

print "Hydrophobic region(s) found in ",
        $count,
        " out of ",
        $sequence_count,
        " sequences.",
        "\n",
        "\n";

This is the output:

AVVAAVMW found at 325
Hydrophobic region(s) found in P30450 | Homo sapiens (Human). | 
NCBI_TaxID=9606; | 365 |    Name=HLA-A; Synonyms=HLAA;

-------------------------------------

VAVLMLCL found at 170
LLALVAIF found at 493
IWICWFAA found at 705
LALALAFA found at 970
Hydrophobic region(s) found in A7MBM2 | Homo sapiens (Human). | 
NCBI_TaxID=9606; | 1401 |    Name=DISP2; Synonyms=DISPB, KIAA1742;

-------------------------------------
Hydrophobic region(s) found in 2 out of 15 sequences.

This is the output I get if I switch them:

Hydrophobic region(s) found in P30450 | Homo sapiens (Human). | 
NCBI_TaxID=9606; | 365 |    Name=HLA-A; Synonyms=HLAA;

-------------------------------------

Hydrophobic region(s) found in A7MBM2 | Homo sapiens (Human). | 
NCBI_TaxID=9606; | 1401 |    Name=DISP2; Synonyms=DISPB, KIAA1742;


LLALVAIF found at 493
IWICWFAA found at 705
LALALAFA found at 970

Hydrophobic region(s) found in 2 out of 15 sequences.` 

Per my teacher's recommendation, I have adjusted my code as follows so that I include everything within the larger while loop and restrict the number of prints with a counter. This new code prints each new header one time, and below it prints each instance of a found region of DNA (essentially flipping what I had before).

New code:

    my $count      = 0;    # here I will count the matched regions
    my $temp_count = 0;    # this I will use temporarily to count

    my $sequence_count = 0;    # here I will count the sequences
                               # that contain a matched region

    if ( $file =~ /(.*;.*;?\n)(\w+)/ ) {

        my $head     = $1;
        my $sequence = $2;

        $sequence_count = $sequence_count + 1;

        # Now I use the sequences that I found, and
        # search them for a hydrophobic region
        while ( $sequence =~ /([VILMFWCA]{8,}?)/gi ) {

            # I use the count variables I made earlier
            # I count all times I match a sequence that has one or more hydrophobic region
            $temp_count = $temp_count + 1;

            # But I don't want the header repeated for the same sequence, so I limit the
            # times that it can print
            if ( $temp_count <= 2 ) {
                print "\n", "Hydrophobic region(s) found in ", $head, "\n";
                $count = $count + 1;
            }

            # I want to know what the position of the match is
            # within the sequence
            my $pos = pos( $sequence ) - 7;
            print $1, " found at ", $pos, "\n", "\n";
        }
    }
}

print "\n",
        "\n",
        "-------------------------",
        "\n",
        "Hydrophobic region(s) found in ",
        $count,
        " out of ",
        $sequence_count,
        " sequences.",
        "\n",
        "\n";

If useful, here is what the file looks like:

>P31946 | Homo sapiens (Human). | NCBI_TaxID=9606; | 246 |    Name=YWHAB;
MTMDKSELVQKAKLAEQAERYDDMAAAMKAVTEQGHELSNEERNLLSVAYKNVVGARRSSWRVISSIEQKTERNEKKQQMGKEYREKIEAELQDICNDVLELLDKYLIPNATQPESKVFYLKMKGDYFRYLSEVASGDNKQTTVSNSQQAYQEAFEISKKEMQPTHPIRL
GLALNFSVFYYEILNSPEKACSLAKTAFDEAIAELDTLNEESYKDSTLIMQLLRDNLTLWTSENQGDEGDAGEGEN
>P62258 | Homo sapiens (Human). | NCBI_TaxID=9606; | 255 |    Name=YWHAE;
MDDREDLVYQAKLAEQAERYDEMVESMKKVAGMDVELTVEERNLLSVAYKNVIGARRASWRIISSIEQKEENKGGEDKLKMIREYRQMVETELKLICCDILDVLDKHLIPAANTGESKVFYYKMKGDYHRYLAEFATGNDRKEAAENSLVAYKAASDIAMTELPPTHPIR
LGLALNFSVFYYEILNSPDRACRLAKAAFDDAIAELDTLSEESYKDSTLIMQLLRDNLTLWTSDMQGDGEEQNKEALQDVEDENQ
>Q04917 | Homo sapiens (Human). | NCBI_TaxID=9606; | 246 |    Name=YWHAH; Synonyms=YWHA1;
MGDREQLLQRARLAEQAERYDDMASAMKAVTELNEPLSNEDRNLLSVAYKNVVGARRSSWRVISSIEQKTMADGNEKKLEKVKAYREKIEKELETVCNDVLSLLDKFLIKNCNDFQYESKVFYLKMKGDYYRYLAEVASGEKKNSVVEASEAAYKEAFEISKEQMQPTHP
IRLGLALNFSVFYYEIQNAPEQACLLAKQAFDDAIAELDTLNEDSYKDSTLIMQLLRDNLTLWTSDQQDEEAGEGN
>P30450 | Homo sapiens (Human). | NCBI_TaxID=9606; | 365 |    Name=HLA-A; Synonyms=HLAA;
MAVMAPRTLVLLLSGALALTQTWAGSHSMRYFYTSVSRPGRGEPRFIAVGYVDDTQFVRFDSDAASQRMEPRAPWIEQEGPEYWDRNTRNVKAHSQTDRANLGTLRGYYNQSEDGSHTIQRMYGCDVGPDGRFLRGYQQDAYDGKDYIALNEDLRSWTAADMAAQITQRK
WETAHEAEQWRAYLEGRCVEWLRRYLENGKETLQRTDAPKTHMTHHAVSDHEATLRCWALSFYPAEITLTWQRDGEDQTQDTELVETRPAGDGTFQKWASVVVPSGQEQRYTCHVQHEGLPKPLTLRWEPSSQPTIPIVGIIAGLVLFGAVIAGAVVAAVMWRRKSSDRK
GGSYSQAASSDSAQGSDMSLTACKV
>Q156A1 | Homo sapiens (Human). | NCBI_TaxID=9606; | 80 |    Name=ATXN8;
MQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
>Q9UQB9 | Homo sapiens (Human). | NCBI_TaxID=9606; | 309 |    Name=AURKC; Synonyms=AIE2, AIK3, ARK3, STK13;
MSSPRAVVQLGKAQPAGEELATANQTAQQPSSPAMRRLTVDDFEIGRPLGKGKFGNVYLARLKESHFIVALKVLFKSQIEKEGLEHQLRREIEIQAHLQHPNILRLYNYFHDARRVYLILEYAPRGELYKELQKSEKLDEQRTATIIEELADALTYCHDKKVIHRDIKPE
NLLLGFRGEVKIADFGWSVHTPSLRRKTMCGTLDYLPPEMIEGRTYDEKVDLWCIGVLCYELLVGYPPFESASHSETYRRILKVDVRFPLSMPLGARDLISRLLRYQPLERLPLAQILKHPWVQAHSRRVLPPCAQMAS
>O75366 | Homo sapiens (Human). | NCBI_TaxID=9606; | 819 |    Name=AVIL;
MPLTSAFRAVDNDPGIIVWRIEKMELALVPVSAHGNFYEGDCYVILSTRRVASLLSQDIHFWIGKDSSQDEQSCAAIYTTQLDDYLGGSPVQHREVQYHESDTFRGYFKQGIIYKQGGVASGMKHVETNTYDVKRLLHVKGKRNIRATEVEMSWDSFNRGDVFLLDLGKV
IIQWNGPESNSGERLKAMLLAKDIRDRERGGRAEIGVIEGDKEAASPELMKVLQDTLGRRSIIKPTVPDEIIDQKQKSTIMLYHISDSAGQLAVTEVATRPLVQDLLNHDDCYILDQSGTKIYVWKGKGATKAEKQAAMSKALGFIKMKSYPSSTNVETVNDGAESAMFK
QLFQKWSVKDQTMGLGKTFSIGKIAKVFQDKFDVTLLHTKPEVAAQERMVDDGNGKVEVWRIENLELVPVEYQWYGFFYGGDCYLVLYTYEVNGKPHHILYIWQGRHASQDELAASAYQAVEVDRQFDGAAVQVRVRMGTEPRHFMAIFKGKLVIFEGGTSRKGNAEPDP
PVRLFQIHGNDKSNTKAVEVPAFASSLNSNDVFLLRTQAEHYLWYGKGSSGDERAMAKELASLLCDGSENTVAEGQEPAEFWDLLGGKTPYANDKRLQQEILDVQSRLFECSNKTGQFVVTEITDFTQDDLNPTDVMLLDTWDQVFLWIGAEANATEKESALATAQQYLH
THPSGRDPDTPILIIKQGFEPPIFTGWFLAWDPNIWSAGKTYEQLKEELGDAAAIMRITADMKNATLSLNSNDSEPKYYPIAVLLKNQNQELPEDVNPAKKENYLSEQDFVSVFGITRGQFAALPGWKQLQMKKEKGLF
>Q9UPA5 | Homo sapiens (Human). | NCBI_TaxID=9606; | 3926 |    Name=BSN; Synonyms=KIAA0434, ZNF231;
MGNEVSLEGGAGDGPLPPGGAGPGPGPGPGPGAGKPPSAPAGGGQLPAAGAARSTAVPPVPGPGPGPGPGPGPGSTSRRLDPKEPLGNQRAASPTPKQASATTPGHESPRETRAQGPAGQEADGPRRTLQVDSRTQRSGRSPSVSPDRGSTPTSPYSVPQIAPLPSSTLC
PICKTSDLTSTPSQPNFNTCTQCHNKVCNQCGFNPNPHLTQVKEWLCLNCQMQRALGMDMTTAPRSKSQQQLHSPALSPAHSPAKQPLGKPDQERSRGPGGPQPGSRQAETARATSVPGPAQAAAPPEVGRVSPQPPQPTKPSTAEPRPPAGEAPAKSATAVPAGLGATE
QTQEGLTGKLFGLGASLLTQASTLMSVQPEADTQGQPAPSKGTPKIVFNDASKEAGPKPLGSGPGPGPAPGAKTEPGARMGPGSGPGALPKTGGTTSPKHGRAEHQAASKAAAKPKTMPKERAICPLCQAELNVGSKSPANYNTCTTCRLQVCNLCGFNPTPHLVEKTEW
LCLNCQTKRLLEGSLGEPTPLPPPTSQQPPVGAPHRASGTSPLKQKGPQGLGQPSGPLPAKASPLSTKASPLPSKASPQAKPLRASEPSKTPSSVQEKKTRVPTKAEPMPKPPPETTPTPATPKVKSGVRRAEPATPVVKAVPEAPKGGEAEDLVGKPYSQDASRSPQSL
SDTGYSSDGISSSQSEITGVVQQEVEQLDSAGVTGPHPPSPSEIHKVGSSMRPLLQAQGLAPSERSKPLSSGTGEEQKQRPHSLSITPEAFDSDEELEDILEEDEDSAEWRRRREQQDTAESSDDFGSQLRHDYVEDSSEGGLSPLPPQPPARAAELTDEDFMRRQILEM
SAEEDNLEEDDTATSGRGLAKHGTQKGGPRPRPEPSQEPAALPKRRLPHNATTGYEELLPEGGSAEATDGSGTLQGGLRRFKTIELNSTGSYGHELDLGQGPDPSLDREPELEMESLTGSPEDRSRGEHSSTLPASTPSYTSGTSPTSLSSLEEDSDSSPSRRQRLEEAK
QQRKARHRSHGPLLPTIEDSSEEEELREEEELLREQEKMREVEQQRIRSTARKTRRDKEELRAQRRRERSKTPPSNLSPIEDASPTEELRQAAEMEELHRSSCSEYSPSPSLDSEAEALDGGPSRLYKSGSEYNLPTFMSLYSPTETPSGSSTTPSSGRPLKSAEEAYEE
MMRKAELLQRQQGQAAGARGPHGGPSQPTGPRGLGSFEYQDTTDREYGQAAQPAAEGTPASLGAAVYEEILQTSQSIVRMRQASSRDLAFAEDKKKEKQFLNAESAYMDPMKQNGGPLTPGTSPTQLAAPVSFSTPTSSDSSGGRVIPDVRVTQHFAKETQDPLKLHSSP
ASPSSASKEIGMPFSQGPGTPATTAVAPCPAGLPRGYMTPASPAGSERSPSPSSTAHSYGHSPTTANYGSQTEDLPQAPSGLAAAGRAAREKPLSASDGEGGTPQPSRAYSYFASSSPPLSPSSPSESPTFSPGKMGPRATAEFSTQTPSPAPASDMPRSPGAPTPSPMV
AQGTQTPHRPSTPRLVWQESSQEAPFMVITLASDASSQTRMVHASASTSPLCSPTETQPTTHGYSQTTPPSVSQLPPEPPGPPGFPRVPSAGADGPLALYGWGALPAENISLCRISSVPGTSRVEPGPRTPGTAVVDLRTAVKPTPIILTDQGMDLTSLAVEARKYGLAL
DPIPGRQSTAVQPLVINLNAQEHTFLATATTVSITMASSVFMAQQKQPVVYGDPYQSRLDFGQGGGSPVCLAQVKQVEQAVQTAPYRSGPRGRPREAKFARYNLPNQVAPLARRDVLITQMGTAQSIGLKPGPVPEPGAEPHRATPAELRSHALPGARKPHTVVVQMGEG
TAGTVTTLLPEEPAGALDLTGMRPESQLACCDMVYKLPFGSSCTGTFHPAPSVPEKSMADAAPPGQSSSPFYGPRDPEPPEPPTYRAQGVVGPGPHEEQRPYPQGLPGRLYSSMSDTNLAEAGLNYHAQRIGQLFQGPGRDSAMDLSSLKHSYSLGFADGRYLGQGLQYG
SVTDLRHPTDLLAHPLPMRRYSSVSNIYSDHRYGPRGDAVGFQEASLAQYSATTAREISRMCAALNSMDQYGGRHGSGGGGPDLVQYQPQHGPGLSAPQSLVPLRPGLLGNPTFPEGHPSPGNLAQYGPAAGQGTAVRQLLPSTATVRAADGMIYSTINTPIAATLPITT
QPASVLRPMVRGGMYRPYASGGITAVPLTSLTRVPMIAPRVPLGPTGLYRYPAPSRFPIASSVPPAEGPVYLGKPAAAKAPGAGGPSRPEMPVGAAREEPLPTTTPAAIKEAAGAPAPAPLAGQKPPADAAPGGGSGALSRPGFEKEEASQEERQRKQQEQLLQLERERV
ELEKLRQLRLQEELERERVELQRHREEEQLLVQRELQELQTIKHHVLQQQQEERQAQFALQREQLAQQRLQLEQIQQLQQQLQQQLEEQKQRQKAPFPAACEAPGRGPPLAAAELAQNGQYWPPLTHAAFIAMAGPEGLGQPREPVLHRGLPSSASDMSLQTEEQWEASR
SGIKKRHSMPRLRDACELESGTEPCVVRRIADSSVQTDDEDGESRYLLSRRRRARRSADCSVQTDDEDSAEWEQPVRRRRSRLPRHSDSGSDSKHDATASSSSAAATVRAMSSVGIQTISDCSVQTEPDQLPRVSPAIHITAATDPKVEIVRYISAPEKTGRGESLACQT
EPDGQAQGVAGPQLVGPTAISPYLPGIQIVTPGPLGRFEKKKPDPLEIGYQAHLPPESLSQLVSRQPPKSPQVLYSPVSPLSPHRLLDTSFASSERLNKAHVSPQKHFTADSALRQQTLPRPMKTLQRSLSDPKPLSPTAEESAKERFSLYQHQGGLGSQVSALPPNSLV
RKVKRTLPSPPPEEAHLPLAGQASPQLYAASLLQRGLTGPTTVPATKASLLRELDRDLRLVEHESTKLRKKQAELDEEEKEIDAKLKYLELGITQRKESLAKDRGGRDYPPLRGLGEHRDYLSDSELNQLRLQGCTTPAGQFVDFPATAAAPATPSGPTAFQQPRFQPPA
PQYSAGSGGPTQNGFPAHQAPTYPGPSTYPAPAFPPGASYPAEPGLPNQQAFRPTGHYAGQTPMPTTQSTLFPVPADSRAPLQKPRQTSLADLEQKVPTNYEVIASPVVPMSSAPSETSYSGPAVSSGYEQGKVPEVPRAGDRGSVSQSPAPTYPSDSHYTSLEQNVPRN
YVMIDDISELTKDSTSTAPDSQRLEPLGPGSSGRPGKEPGEPGVLDGPTLPCCYARGEEESEEDSYDPRGKGGHLRSMESNGRPASTHYYGDSDYRHGARVEKYGPGPMGPKHPSKSLAPAAISSKRSKHRKQGMEQKISKFSPIEEAKDVESDLASYPPPAVSSSLVSR
GRKFQDEITYGLKKNVYEQQKYYGMSSRDAVEDDRIYGGSSRSRAPSAYSGEKLSSHDFSGWGKGYEREREAVERLQKAGPKPSSLSMAHSRVRPPMRSQASEEESPVSPLGRPRPAGGPLPPGGDTCPQFCSSHSMPDVQEHVKDGPRAHAYKREEGYILDDSHCVVSD
SEAYHLGQEETDWFDKPRDARSDRFRHHGGHAVSSSSQKRGPARHSYHDYDEPPEEGLWPHDEGGPGRHASAKEHRHGDHGRHSGRHTGEEPGRRAAKPHARDLGRHEARPHSQPSSAPAMPKKGQPGYPSSAEYSQPSRASSAYHHASDSKKGSRQAHSGPAALQSKAE
PQAQPQLQGRQAAPGPQQSQSPSSRQIPSGAASRQPQTQQQQQGLGLQPPQQALTQARLQQQSQPTTRGSAPAASQPAGKPQPGPSTATGPQPAGPPRAEQTNGSKGTAKAPQQGRAPQAQPAPGPGPAGVKAGARPGGTPGAPAGQPGADGESVFSKILPGGAAEQAGK
LTEAVSAFGKKFSSFW
>Q9NSI6 | Homo sapiens (Human). | NCBI_TaxID=9606; | 2320 |    Name=BRWD1; Synonyms=C21orf107, WDR9;
MAEPSSARRPVPLIESELYFLIARYLSAGPCRRAAQVLVQELEQYQLLPKRLDWEGNEHNRSYEELVLSNKHVAPDHLLQICQRIGPMLDKEIPPSISRVTSLLGAGRQSLLRTAKDCRHTVWKGSAFAALHRGRPPEMPVNYGSPPNLVEIHRGKQLTGCSTFSTAFPG
TMYQHIKMHRRILGHLSAVYCVAFDRTGHRIFTGSDDCLVKIWSTHNGRLLSTLRGHSAEISDMAVNYENTMIAAGSCDKIIRVWCLRTCAPVAVLQGHTGSITSLQFSPMAKGSQRYMVSTGADGTVCFWQWDLESLKFSPRPLKFTEKPRPGVQMLCSSFSVGGMFLA
TGSTDHVIRMYFLGFEAPEKIAELESHTDKVDSIQFCNNGDRFLSGSRDGTARIWRFEQLEWRSILLDMATRISGDLSSEEERFMKPKVTMIAWNQNDSIVVTAVNDHVLKVWNSYTGQLLHNLMGHADEVFVLETHPFDSRIMLSAGHDGSIFIWDITKGTKMKHYFNM
IEGQGHGAVFDCKFSQDGQHFACTDSHGHLLIFGFGCSKPYEKIPDQMFFHTDYRPLIRDSNNYVLDEQTQQAPHLMPPPFLVDVDGNPHPTKYQRLVPGRENSADEHLIPQLGYVATSDGEVIEQIISLQTNDNDERSPESSILDGMIRQLQQQQDQRMGADQDTIPRG
LSNGEETPRRGFRRLSLDIQSPPNIGLRRSGQVEGVRQMHQNAPRSQIATERDLQAWKRRVVVPEVPLGIFRKLEDFRLEKGEEERNLYIIGRKRKTLQLSHKSDSVVLVSQSRQRTCRRKYPNYGRRNRSWRELSSGNESSSSVRHETSCDQSEGSGSSEEDEWRSDRK
SESYSESSSDSSSRYSDWTADAGINLQPPLRTSCRRRITRFCSSSEDEISTENLSPPKRRRKRKKENKPKKENLRRMTPAELANMEHLYEFHPPVWITDTTLRKSPFVPQMGDEVIYFRQGHEAYIEAVRRNNIYELNPNKEPWRKMDLRDQELVKIVGIRYEVGPPTLC
CLKLAFIDPATGKLMDKSFSIRYHDMPDVIDFLVLRQFYDEARQRNWQSCDRFRSIIDDAWWFGTVLSQEPYQPQYPDSHFQCYIVRWDNTEIEKLSPWDMEPIPDNVDPPEELGASISVTTDELEKLLYKPQAGEWGQKSRDEECDRIISGIDQLLNLDIAAAFAGPVD
LCTYPKYCTVVAYPTDLYTIRMRLVNRFYRRLSALVWEVRYIEHNARTFNEPESVIARSAKKITDQLLKFIKNQHCTNISELSNTSENDEQNAEDLDDSDLPKTSSGRRRVHDGKKSIRATNYVESNWKKQCKELVNLIFQCEDSEPFRQPVDLVEYPDYRDIIDTPMDF
GTVRETLDAGNYDSPLEFCKDIRLIFSNAKAYTPNKRSKIYSMTLRLSALFEEKMKKISSDFKIGQKFNEKLRRSQRFKQRQNCKGDSQPNKSIRNLKPKRLKSQTKIIPELVGSPTQSTSSRTAYLGTHKTSAGISSGVTSGDSSDSAESSERRKRNRPITNGSTLSES
EVEDSLATSLSSSASSSSEESKESSRARESSSRSGLSRSSNLRVTRTRAAQRKTGPVSLANGCGRKATRKRVYLSDSDNNSLETGEILKARAGNNRKVLRKCAAVAANKIKLMSDVEENSSSESVCSGRKLPHRNASAVARKKLLHNSEDEQSLKSEIEEEELKDENQPL
PVSSSHTAQSNVDESENRDSESESDLRVARKNWHANGYKSHTPAPSKTKFLKIESSEEDSKSHDSDHACNRTAGPSTSVQKLKAESISEEADSEPGRSGGRKYNTFHKNASFFKKTKILSDSEDSESEEQDREDGKCHKMEMNPISGNLNCDPIAMSQCSSDHGCETDLD
SDDDKIEKPNNFMKDSASQDNGLSRKISRKRVCSSDSDSSLQVVKKSSKARTGLLRITRRCAATAANKIKLMSDVEDVSLENVHTRSKNGRKKPLHLACTTAKKKLSDCEGSVHCEVPSEQYACEGKPPDPDSEGSTKVLSQALNGDSDSEDMLNSEHKHRHTNIHKIDA
PSKRKSSSVTSSGEDSKSHIPGSETDRTFSSESTLAQKATAENNFEVELNYGLRRWNGRRLRTYGKAPFSKTKVIHDSQETAEKEVKRKRSHPELENVKISETTGNSKFRPDTSSKSSDLGSVTESDIDCTDNTKTKRRKTKGKAKVVRKEFVPRDREPNTKVRTCMHNQ
KDAVQMPSETLKAKMVPEKVPRRCATVAANKIKIMSNLKETISGPENVWIRKSSRKLPHRNASAAAKKKLLNVYKEDDTTINSESEKELEDINRKMLFLRGFRSWKENAQ
>Q96KE9 | Homo sapiens (Human). | NCBI_TaxID=9606; | 485 |    Name=BTBD6; Synonyms=BDPL;
MAAELYAPASAAAADLANSNAGAAVGRKAGPRSPPSAPAPAPPPPAPAPPTLGNNHQESPGWRCCRPTLRERNALMFNNELMADVHFVVGPPGATRTVPAHKYVLAVGSSVFYAMFYGDLAEVKSEIHIPDVEPAAFLILLKYMYSDEIDLEADTVLATLYAAKKYIVPALAKACVNFLETSLEAKNACVLLSQSRLFEEPELTQRCWEVIDAQAEMALRSEGFCEIDRQTLEIIVTREALNTKEAVVFEAVLNWAEAECKRQGLPITPRNKRHVLGRALYLVRIPTMTLEEFANGAAQSDILTLEETHSIFLWYTATNKPRLDFPLTKRKGLAPQRCHRFQSSAYRSNQWRYRGRCDSIQFAVDRRVFIAGLGLYGSSSGKAEYSVKIELKRLGVVLAQNLTKFMSDGSSNTFPVWFEHPVQVEQDTFYTASAVLDGSELSYFGQEGMTEVQCGKVAFQFQCSSDSTNGTGVQGGQIPELIFYA
>P0C7T9 | Homo sapiens (Human). | NCBI_TaxID=9606; | 278 |    Name=BZW1L1;
MENSERNKLAMLTGVLLANGTLNASILNSLYNENLVKEGVSAAFAVKLFKSWINEKDINAVAASLRKVSMDNRLMELFPANKQSVEHFTKYFTEAGLKELSEYVRNQQTIGARKELQKELQEQMSRGDPFKDIILYVKEEMKKNNIPEPVVIGIVWSSVMSTVEWNKKEELVAEQAIKHLKQYSPLLAAFTTQGQSELTLLLKIQEYCYDNIHFMKAFQKIVVLFYKAEVLSEEPILKWYKDAHVAKGKSVFLEQMKKFVEWLKNAEEESESEAEEGD
>Q8IYA2 | Homo sapiens (Human). | NCBI_TaxID=9606; | 1237 |    Name=CCDC144C;
MVSWGGEKRGGAEGSPKPAVYATRKTGSVRSQEDQWYLGYPGDQWSSGFSYSWWKNSVGSESKHGEGALDQPQHDVRLEDLGELHRAARSGDVPGVEHVLVPGDTGVDKRDRKKSIQQLVPEYKEKQTPESLPQNNNPDWHPTNLTLSDETCQRSKNLKVDDKCPSVSPSMPENQSATKELGQMNLTEREKMDTGVKTSQEPEMAKDCDREDIPIYPVLPHVQKSEEMRIEQGKLEWKNQLKLVINELKQRFGEIYEKYKIPACPEEEPLLDNSTRGTDVKDIPFNLTNNIPGCEEEDASEISVSVVFETFPEQKEPSLKNIIHSYYHPYSGSQEHVCQSSSKLHLHENKLDCDNDNKPGIGHIFSTDKNFHNDASTKKARNPEVVTVEMKEDQEFDLQMTKNMNQNSDSGSTNNYKSLKPKLENLSSLPPDSDRTSEVYLHEELQQDMQKFKNEVNTLEEEFLALKKENVQLHKEVEEEMEKHRSNSTELSGTLTDGTTVGNDDDGLNQQIPRKENGEHDRLALKQENEEKRNADMLYNKDSEQLRIKEEECGKVVETKQQLKWNLRRLVKELRTVVQERNDAQKQLSEEQDARILQDQILTSKQKELEMAQKKRNPEISHRHQKEKDLFHENCMLQEEIALLRLEIDTIKNQNKQKEKKYFEDIEVVKEKNDNLQKIIKRNEETLTETILQYSGQLNNLTAENKMLNSELENGKENQERLEIEMESYRCRLAAAVHDCDQSQTARDLKLDFQRTRQEWVRLHDKMKVDMSGLQAKNEILSEKLSNAESKINSLQIQLHNTRDALGRESLILERVQRDLSQTQCQKKETEQMYQSKLKKYIAKQESVEERLSQLQSENMLLRQQLDDVHKKANSQEKTISTIQDQFHSAAKNLQAESEKQILSLQEKNKELMDEYNHLKERMDQCEKEKAGRKIDLTEAQETVPSRCLHLDAENEVLQLQQTLFSMKAIQKQCETLQKNKKQLKQEVVNLKSYMERNMLERGEAEWHKLLIEERARKEIEEKLNEAILTLQKQAAVSHEQLAQLREDNTTSIKTQMELTVIDLESEISRIKTSQADFNKTKLERYKELYLEEVKVRESLSNELSRTNEMIAEVSTQLTVEKEQTRSRSLFTAYATRPVLESPCVGNLNDSEGLNRKHIPRKKRSALKDMESYLLKMQQKLQNDLTAEVAGSSQTGLHRIPQCSSFSSSSLHLLLCSICQPFFLILQLLLNMNLDPI
>A7MBM2 | Homo sapiens (Human). | NCBI_TaxID=9606; | 1401 |    Name=DISP2; Synonyms=DISPB, KIAA1742;
MDGDSSSSSGGSGPAPGPGPEGEQRPEGEPLAPDGGSPDSTQTKAVPPEASPERSCSLHSCPLEDPSSSSGPPPTTSTLQPVGPSSPLAPAHFTYPRALQEYQGGSSLPGLGDRAALCSHGSSLSPSPAPSQRDGTWKPPAVQHHVVSVRQERAFQMPKSYSQLIAEWPVAVLMLCLAVIFLCTLAGLLGARLPDFSKPLLGFEPRDTDIGSKLVVWRALQALTGPRKLLFLSPDLELNSSSSHNTLRPAPRGSAQESAVRPRRMVEPLEDRRQENFFCGPPEKSYAKLVFMSTSSGSLWNLHAIHSMCRMEQDQIRSHTSFGALCQRTAANQCCPSWSLGNYLAVLSNRSSCLDTTQADAARTLALLRTCALYYHSGALVPSCLGPGQNKSPRCAQVPTKCSQSSAIYQLLHFLLDRDFLSPQTTDYQVPSLKYSLLFLPTPKGASLMDIYLDRLATPWGLADNYTSVTGMDLGLKQELLRHFLVQDTVYPLLALVAIFFGMALYLRSLFLTLMVLLGVLGSLLVAFFLYQVAFRMAYFPFVNLAALLLLSSVCANHTLIFFDLWRLSKSQLPSGGLAQRVGRTMHHFGYLLLVSGLTTSAAFYASYLSRLPAVRCLALFMGTAVLVHLALTLVWLPASAVLHERYLARGCARRARGRWEGSAPRRLLLALHRRLRGLRRAAAGTSRLLFQRLLPCGVIKFRYIWICWFAALAAGGAYIAGVSPRLRLPTLPPPGGQVFRPSHPFERFDAEYRQLFLFEQLPQGEGGHMPVVLVWGVLPVDTGDPLDPRSNSSLVRDPAFSASGPEAQRWLLALCHRARNQSFFDTLQEGWPTLCFVETLQRWMESPSCARLGPDLCCGHSDFPWAPQFFLHCLKMMALEQGPDGTQDLGLRFDAHGSLAALVLQFQTNFRNSPDYNQTQLFYNEVSHWLAAELGMAPPGLRRGWFTSRLELYSLQHSLSTEPAVVLGLALALAFATLLLGTWNVPLSLFSVAAVAGTVLLTVGLLVLLEWQLNTAEALFLSASVGLSVDFTVNYCISYHLCPHPDRLSRVAFSLRQTSCATAVGAAALFAAGVLMLPATVLLYRKLGIILMMVKCVSCGFASFFFQSLCCFFGPEKNCGQILWPCAHLPWDAGTGDPGGEKAGRPRPGSVGGMPGSCSEQYELQPLARRRSPSFDTSTATSKLSHRPSVLSEDLQLHDGPCCSRPPPAPASPRELLLDHQAVFSQCPALQTSSPYKQAGPSPKTRARQDSQGEEAEPLPASPEAPAHSPKAKAADPPDGFCSSASTLEGLSVSDETCLSTSEPSARVPDSVGVSPDDLDDTGQPVLERGQLNGKRDTLWLALRETVYDPSLPASHHSSLSWKGRGGPGDGSPVVLPNSQPDLPDVWLRRPSTHTSGYSS
>Q96HU8 | Homo sapiens (Human). | NCBI_TaxID=9606; | 199 |    Name=DIRAS2;
MPEQSNDYRVAVFGAGGVGKSSLVLRFVKGTFRESYIPTVEDTYRQVISCDKSICTLQITDTTGSHQFPAMQRLSISKGHAFILVYSITSRQSLEELKPIYEQICEIKGDVESIPIMLVGNKCDESPSREVQSSEAEALARTWKCAFMETSAKLNHNVKELFQELLNLEKRRTVSLQIDGKKSKQQKRKEKLKGKCVIM
>Q8N4W6 | Homo sapiens (Human). | NCBI_TaxID=9606; | 341 |    Name=DNAJC22;
MAKGLLVTYALWAVGGPAGLHHLYLGRDSHALLWMLTLGGGGLGWLWEFWKLPSFVAQANRAQGQRQSPRGVTPPLSPIRFAAQVIVGIYFGLVALISLSSMVNFYIVALPLAVGLGVLLVAAVGNQTSDFKNTLGSAFLTSPIFYGRPIAILPISVAASITAQRHRRYKALVASEPLSVRLYRLGLAYLAFTGPLAYSALCNTAATLSYVAETFGSFLNWFSFFPLLGRLMEFVLLLPYRIWRLLMGETGFNSSCFQEWAKLYEFVHSFQDEKRQLAYQVLGLSEGATNEEIHRSYQELVKVWHPDHNLDQTEEAQRHFLEIQAAYEVLSQPRKPWGSRR

Desired Output

Main Question

I just feel like my original code, although upside down, was more reliable because I didn't have to tell it how many times to print the header, it just looked for and printed only unique headers on its own. Is there a better way to print only new instances of headers but to print all matches of the desired sequence that follows? I could not find a way to specify print only unique matches, and I was uncertain about trying to send all headers and matched regions into a hash (and I have no idea how to do that).

Answer 1

What I did was remove the global modifier from sequence match if statement regex, but leave the modifier after the while statement regex. This way I am not losing the first matches like I was before, but I am still able to print the header before the sequence matches.

    unless (open FILE, "<", '/scratch/SampleDataFiles/test.fasta') {
    die "Cannot Open File", $!;
    }

    $/ = ">";       

    my @file = <FILE>;
    my $file = "@file";
    chomp $file;

    my $count = 0;    
    my $sequence_count = 0;   

    foreach $file (@file) {

               if ($file =~ /(.*;.*;?\n)(\w+)/) {

                   my $head = $1;
                   my $sequence = $2;
                   $sequence_count = $sequence_count +1;

                   if ($sequence =~ /([VILMFWCA]{8,}?)/i) {

                            print "\n", "Hydrophobic region(s) found in ", $head, "\n";
                            $count = $count +1;

                   }


                    while ($sequence =~ /([VILMFWCA]{8,}?)/gi) {

                            my $pos = pos($sequence)-7;
                            print $1, " found at ", $pos, "\n", "\n";

                    }
               }
        }


print "\n", "\n", "-------------------------", "\n", "Hydrophobic region(s) 
found in ", $count, " out of ", $sequence_count , " sequences.", "\n", "\n";



close FILE;

Thanks for your help, guys!

Answer 2

Here's what I would write.

I've made several significant changes

• I use chomp to remove the > from the start of the header of the next sequence, and then check that there are still some non-space character left. The very first record read will be just >, so this discards the empty record

• I've removed the semicolons from your regex pattern, as they don't make much difference, and added some optional whitespace to trim any leading and trailing whitespace on the header

• I've removed the non-greedy modifier ? from [VILMFWCA]{8,} as I didn't see a reason for it. Maybe I'm wrong. I've also changed it so that all matching sequences will be found even if they overlap. Again, maybe that's a bad call: I'm not a bioinformatician!

• Calculating the position of each region as pos() - 7 is wrong as it depends on the length of the match. I've used the built-in array @- instead. $-[1] contains the position of the start of capture $1, $-[2] is for $2etc. and $-[0] is the position of the entire match

• I keep the matching region and its start position in array @regions. When the search is finished I can test whether any were found by checking the size of

use strict;
use warnings 'all';

my $FASTA_FILE = 'test.fasta';


open my $fh, '<', $FASTA_FILE or die qq{Unable to open "$FASTA_FILE" for input: $!};

local $/ = '>';

while ( <$fh> ) {
    chomp;
    next unless /\S/;

    next unless my ( $head, $seq ) = /\s*(.*\S)\s*\n(\w+)/;

    my @regions;

    while ( $seq =~ / (?= ( [VILMFWCA]{8,} ) ) /gxi ) {
        push @regions, [ $1, $-[1] ];
    }

    next unless @regions; # Skip this sequence if no regions found

    printf "%d Hydrophobic region%s found in %s\n",
            scalar @regions,
            @regions == 1 ? "" : "s",
            $head;

    printf "    %s found at %d\n", @$_ for @regions;
}

output

14 Hydrophobic regions found in A7MBM2 | Homo sapiens (Human). | NCBI_TaxID=9606; | 1401 |    Name=DISP2; Synonyms=DISPB, KIAA1742; DGDSSSSSGGSGPAPGPGPEGEQRPEGEPLAPDGGSPDSTQTKAVPPEASPERSCSLHSCPLEDPSSSSGPPPTTSTLQP
    VAVLMLCLAVIFLC found at 88
    AVLMLCLAVIFLC found at 89
    VLMLCLAVIFLC found at 90
    LMLCLAVIFLC found at 91
    MLCLAVIFLC found at 92
    LCLAVIFLC found at 93
    CLAVIFLC found at 94
    LLALVAIFF found at 411
    LALVAIFF found at 412
    IWICWFAALAA found at 623
    WICWFAALAA found at 624
    ICWFAALAA found at 625
    CWFAALAA found at 626
    LALALAFA found at 888