The second snippet shouldn't be any slower. In both snippets, the regexp is compiled once.

However, 

my @regexps = (
   'pattern1',
   'pattern2',
);

for my $s (@strings) {
   for $re (@regexps) {
      something($s =~ /$re/);
   }
}

[download]

is slower than 

my @regexps = (
   qr/pattern1/,
   qr/pattern2/,
);

for my $s (@strings) {
   for $re (@regexps) {
      something($s =~ /$re/);
   }
}

[download]

since the former compiles each regexp for each string, while the latter compiles each regexp once.

In reply to Re^2: Regexes that use a string as basis for matching by ikegami
in thread Regexes that use a string as basis for matching by gatito

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