my @article =  ( 
            'author = {Author, J.P }' ,
            'title  = "A paper about things"' ,
            'etc...'
            );


# iterate over @article array removing all commas
# the commas in the list assignment are gone having
# been used to assign the list elements to the array
# @article so we have no problem with them now.

s/,//g for @article;

# this is the same as
foreach (@article) {
    $_ =~ s/,//g;
}

# in less idiomatic Perl where we do not take advantage of
# the aliasing of array elements to $_ we have to write
for my $i (0..$#article) {
   $article[$i] =~ s/,//g;
}

# to print all the elements of a list 
# on newlines I would normally just write:

print "$_\n" for @article;

# this takes advantage of the aliasing to $_ in a for loop

#  alternatively in long perl
foreach my $stuff (@article) {
    print "$stuff\n";
}

# to join all the edited elements will commas
my $joined = join ",", @article;
print $joined;

##</code><code>##

my $string = <<'STRING';
@article{ 
        author = {Author, J.P } ,
        title  = "A paper, about things" ,
        etc..
     }
STRING
my $open = '';
my $commaless = $1 if $string =~ s/^(\s*@\w+\s*{)//;
for (split //,$string) {
    if (/{|"/ and not $open) {
        $open = /{/ ? '}' : '"';
        $commaless .= $_;
      next;
    }
    $commaless .= $_ unless /,/ and $open;
    $open = '' if $open eq $_;
}
print $commaless;