perl -pe1 file | \
perl -e 'open my $fh, "<", shift; my $line; FH: { $line = <$fh>; my $in; { $in = <STDIN>; redo if $in lt $line }; print $line if $line eq $in; redo }' | \
perl -e 'open my $fh, "<", shift; my $line; FH: { $line = <$fh>; my $in; { $in = <STDIN>; redo if $in lt $line }; if ($line eq $in) { print $line; exit }; redo }'