CODEWITHSUNDEEP
regexperlmatch
user3087867
user3087867

Reputation: 175

Differences between m/PATTERN/ and /PATTERN/ in perl

Is there any technical difference between the following code segments in perl? They seem to behave identical

my $str = "A cat is red";

if($str =~ /cat/) {
    print "Matches\n";
}

vs

my $str = "A cat is red";

if($str =~ m/cat/) {
    print "Matches\n";
}

The difference in this code is the "m" on line 3. Why would someone omit or not omit the "m"?

Upvotes: 13

Views: 4087

Answers (2)

ikegami
ikegami

Reputation: 386396

There is no difference.

/.../ is short for m/.../, just like '...' is short for q'...', and "..." is short for qq"...".

If you're going to use the default delimiter (/ for regex match, ' for single-quoted string literals, and " for double-quoted string literals), you can omit the leading letter(s).

Specifying the leading letter(s) allows you to change the delimiter.

/.../      m/.../     m!...!     m{...}        Match operator
'...'      q'...'     q!...!     q{...}        Single-quoted string literal
"..."      qq"..."    qq!...!    qq{...}       Double-quoted string literal

This can be useful to reduce escaping. For example,

/^http:\/\//

is clearer when written as

m{^http://}

Otherwise, the "m", "q" or "qq" is usually omitted. "s", "tr" and "qw" are not optional.

All of this is documented in perlop.

Upvotes: 11

Mat
Mat

Reputation: 206841

See the RegExp Quote-Like Operators documentation: they're identical. The m "version" allows you to use other characters instead of / as a separator. But apart from that, no difference.

Upvotes: 22

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