Passing bash variable as a pattern to awk

Question

I would like to know how to pass a bash variable as a pattern to awk. I have read several Q/As which tend to answer the same question, how

Answer 1

Variables aren't expanded in regexp literals (/.../). You need to use the ~ operator and string literals.

awk -v pattern="$y" '$0 ~ "^"pattern {print $2}' "$x" > "freec_${x}_${y}_st.txt"

You also need to be careful with any pattern metacharacters/etc. in the pattern.