How to replace condition inside if based on a value of variable

How can a condition inside if block be changed based on the variable value in Perl?

Let's say if $platform value is "window", then evaluation statement of "if ()" must be different, and if $platform value is Linux, evaluation statement of "if()" must be different.

Code Snippet:

my $command;

if ( $platform eq "lnx86" ){
 $command='( $kk eq "qw" ) ';
}
else{
 $command='( $kk eq "we"  ) ';
 
}
my $kk="we";
my $platform=wint;   ## Passed from outside as a command line parameter

if ( $command ) {    ## (Line 13) Here, I want the value of $command to be replaced and if() evaluate the condition after replacement of the variable. Currently, it checks that the $command value is substituted and thus returns TRUE or FALSE. But, desire is that the value of $command must be substituted, and the substituted value must be evaluated.

 print "def\n";
}
else{
  print "nothing";
}

Requirement:

Here, ( on line 13) I want the value of $command to be replaced and if() evaluate the condition after replacement of the variable. Currently, it checks that the $command value is substituted and thus returns TRUE or FALSE. But, desire is that the value of $command must be substituted, and the the substituted value must be evaluated.

Please do provide a suitable assistance.

Thanks in advance!