use strict; use warnings; my $x='11-3-1936'; $x=~ s/(\d+)-(\d\d)-(\d+)/$3-$1-$2/; #2 digit day $x=~ s/(\d+)-(\d)-(\d+)/$3-$1-0$2/; #1 digit day print "$x\n"; # 1936-11-03 $x='2-5-1966'; $x=~ s/(\d+)-(\d)-(\d+)/$1-0$2-$3/; # fix 1 digit day $x=~ s/(\d+)-(\d+)-(\d+)/$3-$1-$2/; # swap order print "$x\n"; # 1966-2-05 doesn't fix single digit month $x='2-5-1966'; $x=~ s/(\d+)-(\d)-(\d+)/$1-0$2-$3/; # fix 1 digit day $x=~ s/(\d)-(\d+)-(\d+)/0$1-$2-$3/; # fix 1 digit month $x=~ s/(\d+)-(\d+)-(\d+)/$3-$1-$2/; # swap order print "$x\n"; # 1966-02-05 ok, but uses 3 regexes $x='2-5-1966'; $x=~ s/\b(\d)\b/0$1/g; # fix any single digit $x=~ s/(\d+)-(\d+)-(\d+)/$3-$1-$2/; # swap order print "$x\n" # 1966-02-05