I'm sure you've already read perldiag, so I'm at a loss what part of that documentation is unclear to you. Maybe you can help us improve the text to make it clearer:

> splain
Possible unintended interpolation of @gmail in string at ./Emailtest_b
+ackup_2.pl line 24.

Possible unintended interpolation of @gmail in string at
        ./Emailtest_backup_2.pl line 24 (#1)
    (W ambiguous) You said something like `@foo' in a double-quoted st
+ring
    but there was no array @foo in scope at the time. If you wanted a
    literal @foo, then write it as \@foo; otherwise find out what happ
+ened
    to the array you apparently lost track of.
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