Yes, closing the filehandle and re-opening for writing with ">" will truncate the file. See open and perlopentut.

Note that you should test open’s return value. Either

use autodie;
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or write

open(my $file1, ">", "testing1.txt") or die "Cannot open file 'testing
+1.txt' for writing: $!";
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Also note that a lexical variable (as shown) is preferable to a bareword for the filehandle.

Hope that helps,