The easiest way is to pass the information via a querystring.
ie. http://hostname/perl/script?a=b&c=d etc.
or in a form.
<form action="/perl/scriptname" method="post">
<input type="text" name="a" value="">
<input type="submit" value="Submit">
</form>

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To retrieve the values it's easiest to use CGI.pm like the following. 
use CGI;
my $q = CGI->new();
my $a = $q->param('a');

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There are many ways to retrieve values. This is the easiest one for me, others may have their own opinion.
There is a lot more you can do with CGI.pm so read the documentation on it.

In reply to RE: Passing Variables in CGI by steveAZ98
in thread Passing Variables in CGI by drujax

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