%regexes = (first => ['(\w+) (\w+) (\w+)', '$1 $3'], 
     second => ['and so on', 'and on'] );

my $string = "big hairy mess";
foreach my $re (keys %regexes) {
     $string =~ s/$regexes{$re}[0]/$regexes{$re}[1]/i;
     print "$re: $string\n";
}