Awk's variable in regular expression

Anyone know how I will use awk's variable in a regular expression?

This line of code of mine is working, the value PREMS should be a variable:

awk '$1 ~ /PREMS/ { if(length(appldata)+2 >= length($1)) print $0; }' appldata=$APPLDATA /tmp/file.tmp

The value of APPLDATA variable is PREMS.

But this line is not working anymore:

awk '$1 ~ /appldata/ { if(length(appldata)+2 >= length($1)) print $0; }' appldata=$APPLDATA /tmp/file.tmp

awk '$1 ~ appldata { if(length(appldata)+2 >= length($1)) print $0; }' appldata=$APPLDATA /tmp/file.tmp

awk '
your awk code goes here
some of it refers to MYVARIABLE
etc.
etc. ' MYVARIABLE=value input_file