IO (files)

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open my $fh, '<', $filename or die "Could not open '$filename' for reading $!";

open my $fh, '>', $filename or die "Could not open '$filename' for writing $!";

open my $fh, '>>', $filename or die "Could not open '$filename' to append $!";

my $line = <$fh>;   # Read a line from a text file