use File::Copy qw(move);

my $source_path = 'C:\Pfad\irgendwas';
my $source_file = 'filename.txt';

chomp( my $target = <STDIN> );

unless( -e $target ){
    move $source_path . '\\' . $source_file, $target;
}
else{
    print "Datei $target schon vorhanden"
}