Tutorials: Basic debugging checklist , brian's Guide to Solving Any Perl Problem

Lets try one of these tips

$ perl -c crates
syntax error at crates line 7, near "foreach @line "
crates had compilation errors.

$ perl -Mdiagnostics -c crates
syntax error at crates line 7, near "foreach @line "
crates had compilation errors (#1)
    (F) Probably means you had a syntax error.  Common reasons include
+:

        A keyword is misspelled.
        A semicolon is missing.
        A comma is missing.
        An opening or closing parenthesis is missing.
        An opening or closing brace is missing.
        A closing quote is missing.

    Often there will be another error message associated with the synt
+ax
    error giving more information.  (Sometimes it helps to turn on -w.
+)
    The error message itself often tells you where it was in the line 
+when
    it decided to give up.  Sometimes the actual error is several toke
+ns
    before this, because Perl is good at understanding random input.
    Occasionally the line number may be misleading, and once in a blue
+ moon
    the only way to figure out what's triggering the error is to call
    perl -c repeatedly, chopping away half the program each time to se
+e
    if the error went away.  Sort of the cybernetic version of S<20
    questions>.

Uncaught exception from user code:
        syntax error at crates line 7, near "foreach @line "
crates had compilation errors.
 at crates line 10.
[download]

Hmm, not so helpful. Ok, next check perlintro and perlsyn, specifically look for instances of foreach

$ perldoc perlintro | grep foreach
        the more friendly list scanning "foreach" loop.
    foreach
            foreach (@array) {
            print $list[$_] foreach 0 .. $max;
            foreach my $key (keys %hash) {

$ perldoc perlsyn | grep foreach
        foreach LIST
    The "foreach" modifier is an iterator: it executes the statement o
+nce
        print "Hello $_!\n" foreach qw(world Dolly nurse);
        LABEL foreach VAR (LIST) BLOCK
        LABEL foreach VAR (LIST) BLOCK continue BLOCK
    The "foreach" loop iterates over a normal list value and sets the
    loop. This implicit localization occurs *only* in a "foreach" loop
+.
    The "foreach" keyword is actually a synonym for the "for" keyword,
+ so
    you can use "foreach" for readability or "for" for brevity. (Or be
+cause
    "foreach" loop index variable is an implicit alias for each item i
+n the
    If any part of LIST is an array, "foreach" will get very confused 
+if you
    "foreach" probably won't do what you expect if VAR is a tied or ot
+her
        foreach $item (split(/:[\\\n:]*/, $ENV{TERMCAP})) {
    Perl executes a "foreach" statement more rapidly than it would the
    Instead of using "given()", you can use a "foreach()" loop. For ex
+ample,
    requires initialization, such as a subroutine or a "foreach" loop.
+ It
[download]

ok, I don't see any "foreach @" uses, so checking http://perldoc.perl.org/perlsyn.html#Foreach-Loops is see lots of examples, but no "foreach @"

That has to be the syntax error, changing that to "foreach $line ($a)"

$ perl -c crates
Global symbol "$line" requires explicit package name at crates line 7.
crates had compilation errors.
[download]

Right, that is strict catching a typo for me, I should write  foreach my $line ($a)

$ perl -c crates
crates syntax OK
[download]

Great , syntax error resolved, next, some other things you should know

perlvar#$a is a special variable, don't use it

Don't use single argument form of open, use the 3 argument form

using perlvar#@ARGV is better thanusing  <STDIN>

$a is a filehandle, but you don't try to readline from it like you do from STDIN

I highly recommend perlintro, http://learn.perl.org/books/beginning-perl/, http://perl-tutorial.org/, Modern Perl