Given what wise haukex already said and considering only your title, a simple oneliner can do the task (pay attention to windows double quotes):

perl -lne "$count+=split}{print $count" /path/file1 /path/file2
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Using Deparse can give you a working starting point to work with:

perl -MO=Deparse -lne "$count+=split}{print $count"  /path/file1 /path
+/file2

BEGIN { $/ = "\n"; $\ = "\n"; }
LINE: while (defined($_ = readline ARGV)) {
    chomp $_;
    $count += split(' ', $_, 0);
}
{
    print $count;
}
-e syntax OK
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That can be translated in: foreach file in the input ( see ARGV in perlodoc ) read it line by line, chomp each line, split the line at withespaces and add the resulting word count to $count When all file processing is finished print the value of $count

L*