use warnings; use strict; my @lines = ; my @splitLines = map {[/('....'..[-\d]*.) -> ('?....'?..[-\d]*.)/]} @lines; my %ends; for (@splitLines) { next if $_->[0] !~/T(?:Dif|Dig)/; $ends{$_->[1]} = $_->[0]; } for (keys %ends) { my $match = "$ends{$_}$_"; @splitLines = grep {"$_->[0]$_->[1]" ne $match} @splitLines; } while (@splitLines) { my $match; for (@splitLines) { next if ! exists $ends{$_->[0]}; $ends{$_->[1]} = "$ends{$_->[0]} -> $_->[0]"; $match = $_; delete $ends{$_->[0]}; @splitLines = grep {$_ ne $match} @splitLines; last; } last if ! $match; } print "$ends{$_} -> $_\n" for sort keys %ends; print "*** $_->[0] -> $_->[1]\n" for @splitLines; __DATA__ 'TAvi' (-37) -> 'TDMk' (-32) 'TAvi' (-38) -> 'TMrk' (-34) 'TDMk' (-32) -> xfer (-12) 'TDif' (-7) -> xfer (-11) 'TDif' (-8) -> 'TMCF' (-35) 'TDig' (-27) -> 'TSpN' (-33) 'TLCI' (-36) -> 'TAvi' (-37) 'TMCF' (-35) -> 'TLCI' (-36) 'TMrk' (-34) -> xfer (-28) 'TSpN' (-33) -> 'TAvi' (-38) 'TSpN' (-33) -> 'TDMk' (-32) 'TSpN' (-33) -> 'TMCF' (-35)