12.24. String Comparisons
If you're trying to compare a string against a fixed number of fixed keywords, the temptation is to put them all inside a single regex, as anchored alternatives: # Quit command has several variants... last COMMAND if $cmd =~ m{\A (?: q | quit | bye ) \z}xms; The usual rationale for this is that a single, highly optimized regex match must surely be quicker than three separate eq tests: Unfortunately, that's not the case. Regex-matching against a series of fixed alternations is at least 20% slower than individually eq-matching the same stringsnot to mention the fact that the eq-based version is significantly more readable. Likewise, if you're doing a pattern match merely to get case insensitivity: # Quit command is case-insensitive... last COMMAND if $cmd =~ m{\A quit \z}ixms; then it's more efficient, and arguably more readable, to write: Sometimes, if there are a large number of possibilities to test: Readonly my @EXIT_WORDS => qw( q quit bye exit stop done last finish aurevoir ); or the number of possibilities is indeterminate at compile time: Readonly my @EXIT_WORDS => slurp $EXIT_WORDS_FILE, {chomp=>1}; then a regex might seem like a better alternative, because it can easily be built on the fly: Readonly my $EXIT_WORDS => join '|', @EXIT_WORDS; # Quit command has several variants... last COMMAND if $cmd =~ m{\A (?: $EXIT_WORDS ) \z}xms; But, even in these cases, eq offers a cleaner (though now slower) solution: use List::MoreUtils qw( any ); Of course, in this particular case, an even better solution would be to use table look-up instead: Readonly my %IS_EXIT_WORD => map { ($_ => 1) } qw( q quit bye exit stop done last finish aurevoir ); |