You assumed the file contains Perl code. Are you sure? I mean are there more lines further down to look and smell like Perl?

In a unix shell like sh or bash (and possibly others) the . (the dot) is an alias for source which executes the contents of a file in the current shell using the current shell as the interpreter. While $1 is the first argument to the command. So, . "$1" in sh/bash means source the file named by the first argument of this command. And the quotes will make it immune to spaces in the filename.

example:

xx.sh:

# file xx.sh
# allegedly perl script
. "$1"
[download]

yy.sh:

# yy.sh a sh script to be executed
echo "hello there i am calling from within yy.sh"
[download]

and in a shell:

$ chmod 755 xx.sh
$ xx.sh yy.sh
hello there i am calling from within yy.sh
[download]

bw, blako