Five common errors in Perl

Time:2019-10-20

I’ve been using Perl + mdbm + spread recently.

PHP has been used for a long time. Python and Ruby have been used together. Perl, the classic scripting language, has never been touched. Now it’s nibbling at textbooks like a primary school student.

It’s really much more difficult to find Perl. Other things didn’t make me make mistakes so often.

1. The first common error is to output content to a file. The standard syntax is:

print STDERR “this is an apple.”;

I usually write

print STDERR,”this is an apple.”;

Always type a comma more. To be honest, I seldom make mistakes repeatedly, but I just can’t remember this place.

2. The second common error is that the arrows referenced by hash are often omitted.

It should have been written

print $hash->{$key};

I often write

print $hash{$key};

3. The third common error is string comparison:

PHP has been used for a long time, always using two equal signs to compare strings. This is wrong. The correct way of writing is

if($var eq “hello”) {
print “world”;
}

I often write:

if($var==”hello”) {
print “world”;
}

This can lead to logic errors that are hard to detect.

4. The fourth common error:

If statements without parentheses (all bad in PHP)

The correct way of writing is:

if($var)
{
print “yes”;
}

I often write

if($var)
print “yes”;

5. There is another error, which is not brought from PHP. It is not expected to be made by ordinary people: missing semicolon.

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