CODEWITHSUNDEEP
regexperl
BryanK
BryanK

Reputation: 1221

alternative to regex pattern foreach value in array Perl

I am checking a regex pattern against each line of STDIN foreach value in an array. I am using the value in the array in the regex pattern. So the example below should match any row that has one of the three numbers in @nums followed by 6 more digits. 

my @nums = qw/
    509
    544
    555
/;

while(my $line = <>) {
    chomp $line;
    foreach my $num (@nums) {
        if ($line =~ /$num\d{6}/) {
            say $line;
        }
    }
}

input

504333322
544009113
509323232
1509868333333
443123432
509999
5599234
410987655

output

544009113
509323232
1509868333333

This is working fine for me, but I would like to know, in order to increase performance, if there is way to do the same thing without the repeated regex matching.

Thank You.

Upvotes: 0

Views: 283

Answers (1)

Kenosis
Kenosis

Reputation: 6204

The following--a variation of TLP's in a comment above--creates a positive lookbehind of alternations using the values in @nums:

use strict;
use warnings;

my @nums = qw/
  509
  544
  555
  /;

my $ORnums = '(?<=' . ( join '|', @nums ) . ')';
my $regex  = qr/$ORnums\d{6}/;

while (<DATA>) {
    print if /$regex/;
}

__DATA__
504333322
544009113
509323232
1509868333333
443123432
509999
5599234
410987655

Output:

544009113
509323232
1509868333333

Hope this helps!

Upvotes: 2

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