Fix #625 Ignore Perl errors from other files

test/handler/test_perl_handler.vader

@@ -0,0 +1,25 @@
+Before:
+  " Switch to the test rails directory.
+  let b:path = getcwd()
+  silent! cd /testplugin/test/handler
+
+  runtime ale_linters/perl/perl.vim
+
+After:
+  silent! 'cd ' . fnameescape(b:path)
+  unlet! b:path
+
+  call ale#linter#Reset()
+
+Execute(The Perl linter should ignore errors from other files):
+  silent! noautocmd file bar.pl
+
+  AssertEqual
+  \ [
+  \    {'lnum': '2', 'type': 'E', 'text': 'Compilation failed in require'},
+  \ ],
+  \ ale_linters#perl#perl#Handle(bufnr(''), [
+  \   'syntax error at ' . b:path . '/foo.pm line 4, near "aklsdfjmy "',
+  \   'Compilation failed in require at ' . b:path . '/bar.pl line 2.',
+  \   'BEGIN failed--compilation aborted at ' . b:path . '/bar.pl line 2.',
+  \ ])