Perl provides two sets of comparison operators; : one set for working with numbers , and one set for working with strings.
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Do not use the number comparison operators on non-numeric nonnumeric strings. Likewise, do not use the string comparison operators on numbers.
Noncompliant Code Example (
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Numbers)
This noncompliant code example improperly uses eq to test two numbers for equality. Counterintuitively, this code prints false.
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The counterintuitive result arises from the fact that because $num is interpreted as a number. When it is initialized, the 02 string is converted to its numeric representation, which is 2. When it is compared, it is convered converted back to a string, but this time it has the value 2, and so the string comparison fails.
Compliant Solution (
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Numbers)
This compliant colution solution uses ==, which interprets its arguments as numbers. Thus this This code therefore prints true, even though the right argument to == is explicitly provided as a string.
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my $num = 02;
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if ($num == "02") {print "true\n"} else {print "false\n"};
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Noncompliant Code Example (
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Strings)
This noncompliant code example improperly uses == to test two strings for equality.
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The == operator first converts its arguments into numbers . This is done by extracting digits from the front of each arguments argument (along with a preceding + or -). Non-numeric Nonnumeric data in an argument is ignored, and the number consists of whatever digits were extract. A string such as "goodpass" has no leading digits , and is thus converted to the numeral 0. Consequently, unless either $password or $correct contains leading digits, they will both be converted to 0 , and will therefore be considered equivalent.
Compliant Solution (
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Strings)
This compliant colution solution uses eq, which interprets its arguments as strings.
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