foreach $FD_NAME ( 1 .. 10) {

        if( $FD_NAME eq $CATEGORY_DATA{$FD_NAME}{'FIELD_NAME'}) { # The if causing prob
           
           #Do my stuff
           
       }
       
} 

print keys %CATEGORY_DATA;


##</code><code>##

%CATEGORY_DATA = (
    1 => ( FIELD_NAME => 'id' ),
    4 => ( FIELD_NAME => 'name' ),
);