s{
(?<=    \{name_a    )
    (?:
        (?:
            (?<=    \s  )
            |
            (?<=    param_[xy]="    )
            (?:
                (?<=    [^"]   )
            )+
            (?<=    "   )
            
        )
        |
        param_[^xy]\w*="[^"]+"
    )+
(?<=    \}  )
}< eaten >gx;

##</code><code>##

s/
\{name_a
    (
        (?:
            [^=\s]+ =  "[^"]*"
            |
            \s+
        )+
    )
\}/ FunAt($1) /gex;

sub FunAt {
    join '', '{name_a ', AtAt(@_) ,'}';
}

sub AtAt {
    my %fun = $_[0] =~ m/([^=\s]+) =  ("[^"]*")/gx;
    return join ' ', map { "$_=$fun{$_}" } grep /param_[xy]/, keys %fun;
}