sub is_integer
{
    return (~$_[0] =~ m/^[0-9]+$/) ? 1 : 0;
}

print "1        ", is_integer(1),       "\n";   # 1 ok
print "'1'      ", is_integer('1'),     "\n";   # 0 ok
print "chr(205) ", is_integer(chr(205)),"\n";   # 1 not ok