you could use a file test operator to check that files exist before they are overwritten. Type perldoc perlfunc at a command prompt and look in the section "Alphabetical List of Perl Functions" to see the full list of file test operators.

print "Save data to what file?";
$filename=<STDIN>; chomp $filename;
if (-s $filename){
warn "$file contents will be overwritten!\n";
warn "$filename was last updated ", -M $filename, "days ago.\n";
}
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-M =returns the age (in days)
-s =returns the size of the data (in bytes)

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