Aqui está uma solução de trabalho. Você pode encontrar a explicação nos comentários.
#!/usr/bin/perl
use warnings;
use strict;
open my $IN, '<', '1.in' or die $!;
my $line;
$line = $_ while <$IN>; # Remember the last line.
my $last = $.; # Remember the number of the last line.
my $interval = (split /\t/, $line)[13]; # Extract the 14th column.
$interval =~ s/[^0-9]+//; # Keep only the number.
seek $IN, 0, 0; # Rewind to the beginning of the input.
$. = 0; # Restart the line counter.
my $start = 1; # Flag to skip first lines.
while (<$IN>) {
my @columns = split /\t/;
/^##/ or undef $start; # Unset start if the header is over.
if (not ($start or $. == $last)) { # Not header or last line?
$_ += $interval for @columns[3, 4];
}
print join "\t", @columns;
}