Check whether the variable is integer.　Perl

is_num.pl

#!/usr/bin/perl
#
sub is_num {
    my ($val) = @_;
    if ( $val =~ /^-?\d+$/ ) {
        return 1;
    }
    return 0;
}
sub test_is_num {
    my ($val) = @_;
    my $res = is_num($val);
    print("$val: $res\n");
}