What warning are you getting, and can you give a small code snippet? I can't even get this code to compile under v5.8.3:

#!/usr/bin/perl

if ('A' EQ 'A')
{
  print "Equal\n";
}
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says:

Bareword found where operator expected at /tmp/test line 3, near "'A' 
+EQ"
        (Missing operator before EQ?)
String found where operator expected at /tmp/test line 3, near "EQ 'A'
+"
        (Do you need to predeclare EQ?)
syntax error at /tmp/test line 3, near "'A' EQ "
Execution of /tmp/test aborted due to compilation errors.
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However, if there is a way to suppress this warning, the manpage for perllexwarn would be the place to look.