In addition to the very helpful comments you've already received, I'd like to point out that, as a rule, I'd "metaquote" the scalar variable in the regex, just in case it contains characters (e.g. +) that otherwise would have special meaning in a regular expression: 

m|\Q$input|o

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For example: 

my $string = '15+2=17';
my $input  = '5+2';
$string =~ m|$input|o;    # Fails
$string =~ m|\Q$input|o;  # Succeeds

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The first match fails because it tries to match one or more 5s immediately followed by a 2. That's because the + is being interpreted as a regexp quantifier, not a literal character.

See the aforementioned perlre, and while you're at it also check out quotemeta.

the lowliest monk

In reply to Re: Perl regular expression question by tlm
in thread Perl regular expression question by Anonymous Monk

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