You call it as every perl script.

bash> perl yourscriptfile
[download]

Or, if the the script includes a shebang-line (#!/usr/bin/perl), make it executable via chmod and

bash> yourscriptfile
[download]

The extension is normally just important for the webserver, and even that is a configuration issue.

On windows the extension is more important, because there the shebang line has no influence on which perl is used. There normally the extension ".pl" is associated with perl.

C:\> yourscript.pl
[download]

However, the first way with explicitly calling the perl interpreter works on both systems.