[pm-h] newbie confusion: executing a perl script

[Russell L. Harris]

At the URL:

    http://69.51.152.43/morse/#GUS-3

I discovered the nifty "KY8D Morse Code Perl Script", which has the
capability of converting any text -- even an entire book -- into Morse
code in a .WAV file, for subsequent conversion into mp3 or ogg vorbis
for use with a personal mp3 player.

(This is one way to circumvent the problem of a book for which the
only available audio edition has been read by someone with a voice you
find intolerable.  If you can find a machine-readable copy of the
book, you can create your own Morse edition.)

The first line of the script is:

    #!/usr/pkg/bin/perl

I am running Debian on an i386, so I used chmod to make the script
executable and I changed the first line of the script to read:

    #!/usr/bin/perl

which works for all the Perl scripts I have been using over the past
year.  But when I attempted to execute the script bash returned an
error message:

    $ ./gus_morse.pl --path ~/scratch/message.txt

    bash: ./gus_morse.pl: /usr/bin/perl^M: bad interpreter: No such
    file or directory

I then consulted the README file supplied by the author of the script,
and saw there the example invocation:

    $ perl gus_morse.pl --path message.txt

which worked.

Would someone kindly explain to me why the "perl ..." invocation
worked, whereas the "./..." invocation did not?

RLH