-Blake

I have the reading in part figured out, :) but how do I substitute the variables for their values (which will change as I run the program)?

I confess that I'm uncertain of the exact question you are asking, so I'll try to answer the easiest question I can make of your post. :-)

Are you asking:

How can I print out the values of scalar variables?

If so, you're in luck. Perl makes this much easier than other C derived languages. The one way to print out values it like this:

print "I like " . $x . "\n";
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This code uses the dot concatentation operator to join strings together. There is a little magic going on here, in that the value of $x is treated like a string. Consider this code:

$x = '0001';
print "I like " . $x;
print "but I like " . ($x + 0)
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The first print statement will yield "I like 0001", but the second prints "but I like 1". The expression with the + operator in the second print statement yeilds a number, rather than a string. Therefore, the leading zeros are removed before the concatentation occurs ($x remains '0001').

Perl provides an even simpler way to print out scalars -- interpolation. Perl will attempt to substitute the value for scalars and arrays in double quoted strings.

$x = '0001';
print "I like $x";
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This code prints "I like 0001". Remember that single quoted strings do not interpolate variables.

$x = '0001';
print 'I like $x';
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This prints "I like $x". You can prevent variable interpolation in double quoted strings by escaping the sigil (the punctuation mark that precedes variable names).

$x = 'timmah!';
print "\$x is $x";
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This prints "$x is timmah!".

For more tips on string interpolation, checkout the perlop manpage under the section "Gory details of parsing quoted constructs".

my @lines = &read_all_lines_into_an_array();

# Here you set the values for the variables you want
# interpolated later...

eval qq{print "$_\n"} for @lines;
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As perl will automatically interpolate the variables for you. However, this approach is *very* dangerous, as you would be trusting "code" coming from outside your script without proper sanity checking. Although the code would only go as far as a print, I would not consider this good programming practice. If you only care for simple scalar interpolation, you can probably do something along these lines:

for my $line (@lines) {
    for my $var ('@scalars_to_interpolate) {
    eval qq{\$line =~ s/\\$var/$var/g}, "\n";
    }
    print $line, "\n";
}
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Regards.