#!/usr/bin/perl -l

my $region1=[[1,2],[5,7]];
my $region2=[[2,6]];

sub max {
    return $_[0] > $_[1] ? $_[0] : $_[1];
}

sub min {
    return $_[0] < $_[1] ? $_[0] : $_[1];
}

sub getIntersect {
    my ($reg1, $reg2) = @_;

    return if $reg1->[1] < $reg2->[0];
    return if $reg1->[0] > $reg2->[1];

    return (max($reg1->[0], $reg2->[0]), min($reg1->[1], $reg2->[1]));
}


foreach my $r1 (@$region1) {
    foreach my $r2 (@$region2) {
        if( my @is = getIntersect($r1, $r2) ) {
            print "[$is[0], $is[1]]";
        }
    }
}
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