"Interpolation and escaping" can become the sort of issues that cause a seasoned programmer to look at you with an expression that vaguely resembles table-tennis, because in her (or his) own mind that's rather-exactly what's going on at the time.
If you have a literal string with "magical" characters in it, such as
5a@Wf7$X, then your Perl program needs to change that string
into a character sequence that the
shell program, upon receiving it, will change
back into the original!
(Take a moment to let the "ping-pong look" come and go...)
So what
you need to do is to take a string that looks like
this...
5a@Wf7$X
... and make it look like
this...
5a\@Wf7\$X
... so that the shell-program you wish to run can change it
back to the original ...
5a@Wf7$X
(Actually,
the shell itself performs this service...)
So, what
you need to do is to "escape" the string that you've been given so that the shell can then "un-escape" it back into the original string.
Something like this extemporaneously-written bit of chicken-scratching might do it:
$foo =~ s/[@$\]/\\\1/g; (ooh, ick!) might do it...
Let me
try to explain...
- The syntax $foo =~ regexp applies a regular-expression against the variable $foo.
- The regular-expression is of the form s/change_from/change_to/globally...
- The change_from part is "either of the two characters '@' or '$' or '\'"
- The change_to part is 'a literal backslash character' followed by 'whatever character you found.'
If you are
extremely lucky, you will happily find that this regular-expression transforms your string consistently
into a string that will eventually be transformed
back to the original string.
Fun stuff, huh?