I don't get how the lines after system() are going to work with the data, but you could do something like:

    opendir( DIR, $targetdir ) || die $!;
    my @files = grep{ /\.sf$/ } readdir( DIR );

    ## do interesting stuff with @files
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If you are supposed to receive a real shell-expanded text, like /foo/bar/*.sf, then use a glob

   ## when passing something like *.pl, make sure
   ## to single quote it so that the shell doesn't
   ## automatically expand it:
   ##
   ##    scrip.pl '/foo/bar/*.pl'
   ##
   my @entries = <$ARGV[0]>;
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