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How can I understand the following usage of the open() function in Perl File I/O?
open(FHANDLE, ">" . $file )
I tried to find this type of syntax in the docs but did not find; please note there is a . (dot) after ">".
All I cannot understand is a use of dot, the rest I know.
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The period . is the concatenation operator. The equal sign to the right means that this is an assignment operator, like in C. For example: $input .= $_; Does the same as $input = $input .
=~ is the Perl binding operator. It's generally used to apply a regular expression to a string; for instance, to test if a string matches a pattern: if ($string =~ m/pattern/) {
$_ - The default input and pattern-searching space. @_ - Within a subroutine the array @_ contains the parameters passed to that subroutine. $" - When an array or an array slice is interpolated into a double-quoted string or a similar context such as /.../ , its elements are separated by this value.
The variables are shown ordered by the "distance" between the subsystem which reported the error and the Perl process...$@ is set if the string to be eval-ed did not compile (this may happen if open or close were imported with bad prototypes), or if Perl code executed during evaluation die()d.
This is an example of the old, two-argument form of open (which should be avoided now that three-argument open is available). In Perl, . is the append operator. It combines the two strings into a single string.
The line of code you posted is equivalent to open(FHANDLE, ">$file" ), it just uses a different method of combining the > and $file.
The better way to do it these days would be open(my $fhandle, '>', $file), as shown in the documentation you linked to.
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