use strict; use warnings; my %groups; #my @keys; while(){ s/(\s|#)\d\s/$1/g; s/\s//g; my( $key, $left, $right ) = /^([^#]+).*#(.*)<=>(.*)/; $groups{$_}{left }{$key} = 1 for split /\+/, $left; $groups{$_}{right}{$key} = 1 for split /\+/, $right; #push @keys, $key; } for my $grp ( values %groups ) { for my $left ( keys %{ $grp->{left} } ) { for my $right ( keys %{ $grp->{right} } ) { print "$left <=> $right\n"; } } } __DATA__ R00009MM#R00009#2 C00027MM <=> C00007MM + 2 C00001MM R00014MM#R00014#C00022MM + C00068MM + C00080MM <=> C05125MM + C00011MM R00081MM#R00081#C00007MM + 4 C00126MM + 8 C00080MM <=> 4 C00125MM + 2 C00001MM + 4 C00080Cyto R00086MM#R00086#C00008MM + C00009MM + 7 C00080Cyto <=> C00002MM + C00001MM + 7 C00080MM R00094MM#R00094#2 C00051MM + C00003MM <=> C00127MM + C00004MM + C00080MM