problem with regular expression in parameters started from '^'

[tumikosha]

parameterr: reg_exp {
    type: string
    default_value: "^(Act|(.*_Act))[A-Z]{1}[^_]*$"
  }


  derived_table: {
    create_process: {
      sql_step:

     -- regexp  {% parameter agg_poc_src.reg_exp %}

     ;;

If the parameter  is selected the filter correctly show the first character

     -- regexp '^(Act|(.*_Act))[A-Z]{1}[^_]*$'

If the parameter is not selected the filter has lost the first character
     -- regexp '(Act|(.*_Act))[A-Z]{1}[^_]*$': 

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