Unfortunately not all functions will send back the contectula meaning you think it implied. Different list returning functions will return different things when returning scalars. localtime will return a join of it's array; readline ( and likewise <> ) will return the 'next' value in the series ( mainly I think, because it's designed to be iterative ); Others may return the array and default to the scalar value as you had thought about the <> statement

I believe the important thing would be to not make assumptions. Once you get to know which returns which, you might be tempted to make accomodate each. I myself would stick to what I know would work, in this case return an array, then use scalar to get the count

....
my @lines = <$fh>;
my $count = scalar @lines;
....
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That also tends to allow others reading your code to understand your code, especially if they still do not know the ins and outs of contextual returns.

As far as reading the file, slurp works well and I won't dispute it's usefulness, but I am still old school.

# Unstested
my strict;
my warnings;

my $content = '';
my $filename = 'myfile.txt';
{
  local $\;
  open $fh, '<', $filename or die "Cannot open $filename: $!\n";
    $content = <$fh>;
  close $fh;
}
print $content;
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Here we localize the input record seperator, or enable 'slurp' mode, and the call using <> will pull in the whole file.